What is Thatch?
Thatch is just dead grass and roots that forms a layer on the top of the rootzone but how many headaches does it give the sports turf manager? It causes disease, dry patch and fairy rings, water retention, black layer, poa annua ingress, and slow playing surfaces that seem to eat fertiliser, water, fungicides and top dressing.

A hectare of grass with 4cm of thatch has 400m3 of dead organic matter to degrade. The aim of the Symbio programme is convert this organic matter to plant food and humus.

Thatch holds water and prevents oxygen from reaching the rootzone this causes Black Layer

Black Layer

Black layer on heavily watered stadium football pitch

Black layer only occurs in anaerobic soil conditions i.e. where there is no oxygen. – Anaerobic bacteria produce hydrogen sulphide gas from the sulphates applied with most inorganic fertilisers. Hydrogen sulphide smells of rotten eggs and can combine with iron and magnesium to form highly toxic compounds. Before black layer appears toxic butyric, acetic and valeric acids are formed along with alcohol all of which kill the root system - this is a main cause of roots not penetrating overwatered soils.

If you aerate with a sorrel roller or microtines every two-three weeks, follow the programme set by your qualified Symbio advisor and do not see a reduction in thatch or nutrient input on any green or pitch, Symbio will analyse the problem and provide free ThatchEater until the thatch starts to degrade (UK only, unless agreed with Symbio)

Apply Symbio ThatchEater in Spring at 50gms per M2 when the soil temperature is above 6oC during spring renovation or microtining - brush the ThatchEater into the tine holes or mix with top dressing. Do not apply below the thatch layer. One application of Symbio ThatchEater works for up to six months possibly more in extended growing seasons

Aerate with a sorrel roller as often as possible. If the grass looks like it needs a fertiliser application aerate first. The extra oxygen may kick start biological degradation and release enough nutrients. If the grass needs fertiliser we recommend applying low levels of liquid fertiliser at no more than 10Kg N per hectare per application. Apply Liquid Aeration at 1 litre per hectare during the autumn, winter and spring when the rootzone is wet. If black layer is apparent tine to the black layer so that the active ingredients flood the black layer

Full programme application

Nutrition (see Soil Biology and Chemistry Analysis)
Thatchy greens usually have a lot of poa annua which is slow to start growing in spring so a base fertiliser of Symbio MycoGro 5.0.29+4Mg with mycorrhizae, thatch reducing fungi and phosphate solubilising bacteria is a good start. If the spring is late then a mix of calcium, magnesium and potassium nitrate to balance base saturation and provide readily available nutrient for the poa annua could be applied first during a warm spell.

Once Thatch Eater has been applied nutrient will be released as the thatch breaks down, sorrel rolling may be all that is needed for nutrient release. Fertilise to maintain even growth and roll only. You may not need to apply fertiliser for several months, or you may need light additions of liquid fertilisers. If the growing season is long a granular like MycoGro 10.0.10+4Mg may be applied.

USGA specification greens typically need between 40Kg N and 80Kg N per hectare in the first year of thatch reduction the rest coming from nutrient released from the thatch.